“Our study provides direct evidence showing the significance of these foot muscles in supporting the performance of the human foot.

“Contrary to expectations, PIMs contribute minimally to supporting the arch of the foot during walking and running.

“However, these muscles do influence our ability to produce forward propulsion from one stride into the next,” Farris said.

For the study, reported in the Proceedings of the National Academy of Sciences (PNAS), the team compared foot and lower limb movement with and without a nerve block that prevented contraction of these muscles.

During ground contact in walking and running, the stiffness of the foot arch was not altered by the block, showing that the PIMs’ contribution to arch support is minimal, probably due to their small size.